Lens mounting and film support for microfilm apparatus



May 19, 1953 v. E. PRATT ETAL LENS MOUNTING AND FILM SUPPORT FOR MICROFILM APPARATUS 5 Sheets-Sheet l Original Filed March 7, 1947 Nl .DNIN

W//MILIl Uil ///////m May 19, 1953 v. E.' PRATT ETAL LENS MOUNTING AND FILM SUPPORT FOR MTCROFILM APPARATUS original Filed March '7, 1947 5 Sheets-Sheet 2 f@ AMAA. ALF-WOM Qn-7o F. e BY M www@ ATTORNEYS May 19, 1953 v. E. PRATT ETAL 2,638,812

LENS MOUNTING AND FILM SUPPORT FOR MICROFILM APPARATUS Original Filed March 7, 1947 3 Sheets-Sheet 3 SMEEMQEE-EQ mmmmm Patented May 19, 1953 UNITED STATES PATENT OFFICE LENS MOUNTING AND FILM SUPPORT FOR MICROFILM APPARATUS Verneur E. Pratt and George F. Gray, Norwalk, Conn.

6 Claims. l

This invention relates to lens mounting and film support for microfilm apparatus and more particularly to such mountings for use in microfilm devices such as those disclosed in U. S. Patents #2,435,099 dated January 27, 1948 and #2,478,980 dated August 16, 1949 and is a division of the co-pending application Serial Number 732,971, filed March 7, 1947, now U. S. Patent Number 2,538,269, dated January 16, 1951.

An object of this invention is to provide a lens mounting combined with a film support.

Another object is to provide a lens mounting with a slit forming member forming part of the mount.

Another object is to provide a lens mounting wherein two lenses may be employed in side-byside relation to produce a double row of images on a film.

A further object is to provide a combined lens mount and film support that will eliminate troubles now encountered due to temperature changes in the apparatus.

Other objects and advantages will be pointed out hereinafter particularly in connection with the following brief discussion of the prior art necessary to a proper understanding of the invention.

While the following specification and accompanying drawings disclose, by Way of illustration preferred embodiments of the invention, it will be understood that many changes can be made from what is herein shown without departing from the invention as defined in the appended claims.

In the accompanying drawings:

Figures 1 and 2 are diagrammatic views of prior art lens mounts and their associated film supports or gates for the purpose of illustrating certain features of prior art construction in order to clearly understand the advantages and construction of the instant invention, and how it distinguishes from such prior art;

Figure 3 is a front view of a lens mount embodying the invention;

Figure 4 is a side view of the lens mount shown in Figure 3;

Figure 5 is a detail view of a roller that can be applied to the lens mount shown in Figures 3 and 4 and 6;

Figure 6 is a front view of an alternate form of lens mount embodying the invention;

Figure 7 is a plan view of a lm made by a camera employing the lens mount of Figure 8;

Figure 8 is a side view of a twin-lens mount embodying the invention; and

Figures 9 and 10 are details of the mount shown in Figure 8.

In Figure 1 is shown a lens mount and film support (often termed a film gate) and illustrates diagrammatically a construction in common use. The framework of a camera is indicated at I0 and this supports a horizontal member I I upon Which the lens I2 is mounted.

The film support comprises a fixed platen I3 secured to the frame I0 having an opening (or a glass I4 therein) upon which the film F is supported and towhich it is pressed by a pressure plate l5 which is hingedly or otherwise movably supported on frame I0.

It will be understood that the pressure on the film is removed when the film is moved, the member I5 usually being intermittently raised by suitable mechanism (not shown) to permit of such film movement.

In such arrangements it is necessary Very accurately to construct or assemble all parts shown to obtain and maintain the dimensions N and Y. These and other difliculties will be discussed in connection with Figure 2.

The device Figure 1 can be used in flow cameras where the photographing is done with the film in motion, provided the pressure plate I5 is urged toward the film with a light touch insufficient to scratch the film support or base.

The construction shown in Figure 1 is open to other serious objections and limitations which need not be discussed here but which are well understood and which brought into being the construction shown in Figure 2 which is in extended use in the microfilm field, and particularly to flow cameras.

Referring to Figure 2, a revolving drum I6 is mounted in bearing I I supported in the frame IIJ. The lm is supported on this drum and is moved across the back focus of lens I2 by the rotation of the drum or by any other suitable means. Details of devices employing this type of construction are shown in the aforesaid patents previously mentioned.

In practically all types of microfilm cameras such as referred to above and in the aforesaid patents, the copy support for the copy 2| is secured to or forms part of the framework I0 of the camera, so as to support the copy 2| in the front focus of the lens I2.

A suitable source of illumination is provided for illuminating the copy so that in the manner common to all cameras of this description, the lens of the camera receives the light reflected from the copy on the copy support and an image 011 the lm in the rear focus of the lens is produced in the usual manner.

While the construction shown in Figure 2 does not have some of the limitations and objections of that shown in Figure 1, it inherently has certain objectionable features in common therewith. Among these (an-d the objects of the instant invention are their elimination) are:

(A) Much of the trouble in making production cameras to make high resolution microlm is in holding tolerances on the drums IS. A run-out eccentricity of .0015 inch on factory production does not give satisfactory results, and in a certain commercial device a limit of run-out of .0003 inch is obtained by diiiicult and expensive selection and manufacturing and assembling..

This run-out aifects the dimension N of Fig. 2 which corresponds to the dimension N of' Fig. 1 and is the critical distance between the sensitive emulsion surface of film F and the nodal? point of the lens l2, a very critical dimension in shortfocus. lenses and a. dimension that is adjusted to a fraction of a mm.

In'making these drums lB therefore, it is necessary to havey them concentric with axis yai to keep the diameter d the same on all drums and to have the shaft I8 supporting the drum perpendicular tothe inner face of the support I0.

(YB) To maintain the dimension N on commercial machines so as to makev various lens mounts interchangeable, it is obvious that the axis ai` of the drum. shaft must be properly spaced from the outer surface Ila. of the lens support. This means careful machining and location of the member Il, the bearing I1 in frame l0, the bore in the bearing for `the shaft I8, and the bore in the hub I9 of the drum I6.

Care is also necessary with the construction of Figure l as to the machining and relative location of the supports I3 and Il andthe pressure plate bearing support 2 0.

(C) As yet, no way has been found, granted that the difliculties of manufacturing and assembling have been overcome, to compensate for the coefficient of expansion of aluminum or other metal frame members i0'. Under operating conditions with a 50 F. differential, the dimension b may vary as much as .-0005- inch, which seriously and adversely affects the resolution.

(D) With the construction shown in Figure 2, variations in the thickness-.of the emulsion on the film varies the dimension C, thereby causing a variation in the important dimension N.

From the foregoing it can be readilyseen that tol obtain the accurate dimensions necessary inhigh resolution microfilm apparatus, it is necessary to work to close tolerances. Now, if in a givenl machine all tolerances. are plus, the device would not produce good' microfilm.. Thisy has necessitated' careful and expensive: inspection and selection of parts and much hand fitting, and has made the interchanging of lenses between machines in factory assembly very difficult and: expensive.

(E) As it is. diiiicult to maintain accurate dimensions in these machines, it has beenA cus-- toma-ry to equip them withk lenses such as shown` at i2 which can befocussedso that the user can focus ,the lensV and thereby adjust the critical dimension N if for any reason -of manufacturing or assemblyv it is not correct.

Now, these short-focus lenses. require focussing (between nlm and lens)v to: the thousandth of an inch-and. adjustment which can] only be made by an expert having proper equipment and. exi-- perience. Suche a focussing ope-ation isl usually entirely beyond the ability of the averageV opvproperly see to` focus the lens.

e erator of the machine. It is therefore highly desirable to employ fixed focus lenses which can be easily -changed in any given machine (or between machines) and which are focussed at the factory and never require subsequent focussing as they are pre-focussed.

It is difficultin fact commercially impractical-to do this with the lenses mounted as shown in Figures 1 and 2 or in any other known manner, as the space behind the upper face of the lensy mount and the film in some cameras is less than 5 mm., and the image of the copy 2| made by the lens on the film F cannot be observed, and even if seen is so small and in slit form that no one, even with a microscope, can

Focussing, therefore, must be done on a trial-and-error basis by making sample film at various lens locations, processing said film, and by microscope examination selecting the best focus position and resetting the lens finally to that chosen best focus position. Such an operation obviously cannot be performed by the user of the machine, so interchangeable fixed focus lenses are not only highly desirable but are a practical necessity'.

Referring now to the instant invention, Figure 3 shows a lens mount embodying same. Here the framework I0 of the camera supports a turret or len-s: mounting frame 22 in which isv mounted the lens system 23. rihe lenses may be adjustable in the mounting for convenience in. assembly but once assembled, are never again. adjusted.

An-,arm 2li' isvertically adjustable in the mounting. 22' and is held therein by any suitable means such as' the screw 2'5. This arm has a horizontally extending platen 26 secured thereto which overl'ies the cap 2l of the mounting, said cap having the slit 23 therein.

'The nlm F restsv against the bottom arcuate surface of platen 20 with its emulsion side towardthe lens. Byy adjusting the arm 2li, the critical dimension N-the distance between the lm andlens-is. adjusted and once this is accomplished, the adjustment isv fixed'. Such adjustment can be `made with the lens mount out of the camera. The iii-m is. fed' across the platen 2E in any suitable manner such, for example. as that showny in the aforementioned Patent #2,435,099.

The roller Siti may be guide rollers or feed rollers and may be mounted on the framework i0 ofthe camera and it will be noted that no particular' accuracy in spacing them from the base of frame i0y (the dimension Y, Fig. 3) is necessary, as all critical dimensions are taken care of in the lens mount assembly which not only supports the lens, but also supports on thev same assembly, the film: in 'xed relation: to the lens.

The platen Zit may be made of or faced with carbaloy or agate or some other hard noni-wearing material, or may have therein a rol-ler 30, Figure 5, against which the nlm F is heidi tautv by the film-feeding mechanism, so that the roller revolves in a suitable bearing in the platen 20. This roller may help to reduce friction on the film during its traverse across thev platen 26 while it receives images in the back focus of. lens Z3.,

The construction just described eliminates the d-iieulties discussed in connection with paragraphs A and B hereof.

Theconstruetion shown in Figures 3 toy 5 inelusive eliminates precisionvvork on the iilm drivek and supporting parts of the camera and confines it to the lens mount per se. This being a relatively small device, it is not seriously affected by temperature changes as discussed under paragraph C hereof.

The construction shown in Figures 3 to 5 inclusive does not eliminate troubles due to variations in the thickness of lm stock or the emulsion thereon, as discussed under paragraph D hereof.

To eliminate difficulties due to variations in the film thickness C construction shown in Figure 6 may be employed. Here the platen supporting the film F takes the form of an arcuate cap having the slit 32 therein transverse the film. Here the critical distance N is between the outer surface of the emulsion on lm F and the nodal point of the lens 23 and, because of the relatively small dimensions of the one-piece turret 33, this dimension can be made very accurately at low cost.

The platen block 3| can be made of any suitable material, same as the platen 26, Figures 3 and 4, and the slit 32 may have rollers at each side thereof, similar to roller 30, Figure 5.

The film F overlies the platen 3| and is held against same by any suitable film-feeding mechanism. If desired, a Weight or spring-pressed member can be supported either on the turret 33 or on the frame I to overlie the lm F Figure 6 in order to press the film down against the slit in the arcuate cap 3 I. Such a member resembles member 26 of Figure 3 and can be of any suitable construction as its only purpose is to gently press the lm against the cap 3| so that same always remains in contact therewith, covering the slit 32. Variations in the thickness of the film stock or emulsion cannot change the critical dimension N, Figure 6.

As the lips of the slit 32 are in contact with the film, the opening against the film is clearly dened. A typical slit may be .080 inch wide by 1% inches long, and the curvature of the top of platen cap 3| may be on a 21/2 inch radius.

Because of the extreme accuracy that can be attained in a lens mount constructed in accordance with the instant invention, a double lens mount for making twin rows of 15 mm. images on one width of 35 mm. film can be easily and cheaply constructed to be interchangeable with the 35 mm. single-row-one-lens mount previously described, and for use in the same camera to produce duplicate micro-photographs side-by-side of the same copy.

Such twin-images are shown in Figure 7 Wherein 34 denotes the film and each pair of duplicate images are shown at a, a1, b, b1, c, c1, d, d1, e, e1. Such a film is made in a iow camera by feeding copy a, for example, through the camera and making two simultaneous exposures via the twinlens to produce images a, a1, etc. To produce such twin images with a single lens camera would require feeding the copy to complete row 35, then re-winding the film and again feeding the copy to produce row 36, or a twin-sided camera must be used, each camera complete With lens, and each loaded with a separate 16 mm. lm. The result is two 16 mm. negatives exactly alike. With the 35 mm. film shown in Figure 7 it is only necessary to photograph once in a single camera then slit the film longitudinally along line 31 and remove 1'1/2 mm. from each edge toy produce the duplicate negatives.

Obviously, the 35 mm. negative film can be used to print positives, which are then split at 31 to produce duplicates.

The twin-lens mount will rst be described as applied to existing cameras having drums I6 as described in connection with Figure 2. Such cameras are described in the aforesaid Patent #2,478,980.

Referring to Figure 8, the lens mount 38 supports the lenses 39, 40. The lenses must be exactly the same focal length in order that the rows 35, 36 (Figure 7) of images can be brought into flow at the exact ratio of movement of im to copy. The lenses in Figure 8 may have a back focal length of 210 mm. in which case the space between the face of the cap 4| having the twin slits 42, 43 therein, is about 5 mm.

As shown in Figure 9, the slits are each .050 inch wide and suiciently long to form an image of the desired Width to t on the 16 mm. film strip produced by slitting the 35 mm. strip as previously described.

A baille 44, Figure 10 extends transverse the cap between the slits to insure that the twin images do not overlap. This may extend downward into the mount 38 about .170 inch, and may be about .095 inch thick, 1/8 inch Wide at the bottom and 1A inch wide at the top-tapered as shown in Figure 10.

The cap 4| is close to the emulsion side of the film F (the drawing Figure 9 is merely diagrammatic) and the division or baille 4| therefore acts as a mask and not as a vignetter or diaphragm.

While the arrangement shown in Figure y8 does not eliminate all of the difficulties listed under paragraphs A, B, C and D hereof, it is useful in that old cameras can be used to make the film shown in Figure '7 merely by substituting the twin-lens mount of Figure 8 for the existing single lenses therein.

Width of the fields of view 45,146 of the lenses Figure 8 transverse the direction of flow are sufficient to include copy such as documents, etc., 14 inches wide when located in the focal plane of these lenses, and of course this depends upon the characteristics such as focal length, etc. of the lenses.

To obtain the advantages set forth in connection with the lens mounts, Figures 3 to 6 inclusive, with a twin-lens mount as shown in Figure 8, it is only necessary to modify the twinlens mount as shown in said Figures 3 to 6 inelusive.

For example, the mount Figure 8 may have the arm 24 and platen 26 of Figures 3 and 4 with or without the roller 30 of Figure 5; or the mount Figure 8 can have the arcuate platen 3| on which the lm F is supported as described in connection with Figure 6.

All of the new lens mounts herein described may be removably mounted on the camera frame I0. This may be accomplished in any suitable manner, such as by the provision of the gibs 45, Figure 3, the base 46 of the mount being tapered as shown so that the mount can be pushed into the gibs and held between them and against vertical movement. A stop 4i can be secured to the frame U (Figure 8.) to aid in positioning the lens mount in the camera.

As the single and double lens mounts can be made interchangeable, they can be used at will n any given camera and are readily interchangeable among cameras on a production line in the factory without the necessity of any re-focussing.

As the distance between the lens and film are fixed within the mount itself, mounts of the type shown in Figures 3-6 inclusive and the twin lens mount as shown in Figure 8 modified in accordance with the disclosure of Figure 6 can be mounted on an optical bench or its equivalent and the lens-to-nlmdistance N very accurately adjusted in a manner that cannot be accomplished in photographic devices wherein the lens is mounted on one part of the framework and the nlm supported on another, as described in connection with Figures 1 and 2. The invention therefore eliminates much of the precision work heretofore necessary and which made it not only dliiiicult to interchange lenses in any given camera, but made it practically impossible to change lenses between cameras without having to re-iocus the lens.

The feeding elements for feeding the nlm from one reel to another may be of any desired type, such for example as those shown in the aforesaid patents. It will be noted that the slit form-ing member such as the caps 3| or 4l is located between the feeding elements that drive the nlm and between which the nlm is tensioned. rihese caps therefore, press upon and displace the tensioned nlml in aplane perpendicular to the path of travel of the nlm, the latter being held Vagainst the slit or slits which therefore define the area or exposed areas on the nlm, which is preferably emulsion side down on the cap.

What is claimed is:

1. In a micronlm camera employing moving nlm and adapted to move said film across a photographic zone, in combination, a supporting frame member, means on said supporting frame member forming a transverse slideway in predetermined spaced relation with said zone, lens mounting means normally slidably retained in said slideway, a pair of substantially parallel lenses secured in said lens mounting means in predetermined spaced relation with said slideway, said mounting means carrying said lenses being slidable along said slideway into and out oi said camera, and stopl means on said frame member adapted to engage said mounting means for positioning said lenses in side-by-side operative optical alignment with said nlm in said zone a copy feeder and means for moving same in synchronism with said moving nlm, said lenses being focussedon copy carried on said feeder to produce images of said copy in side-by-side relation on said moving nlm, said copy comprising separate sheets of paper carried on said feeder.

2. The combination claimed in claim l wherein said lens mounting means includes a unitary structure having outwardly extending side portions engaging said slideway, said slideway-forming means including parallel rails having portions overlying said outwardly extending side portions of said lens mounting means to restrain the same from movement toward said zone.

3. The combination claimed in claim 1 including screening means on said lens mounting means between said lenses and said nlm, said screening means having a narrow slit disposed transversely of said nlm between each of said lenses and said nlm and aligned optically with said lensesk and said photographic zone when said mounting means is in engagement with said stop.

4. A lens mount for use in micron-lining lapparatus wherein a moving nlm is employed, said apparatus including a horizontally disposed copy iced-- er to feed sheet copy past lenses nxed in relation to said copy and nlm in timed relation to movement of said nlm; said lens mount comprising a frame adapted to be positioned removably in said apparatus; a pair of lenses secured to said frame and 'focussed on a moving sheet on said 'copy feeder to form images of said sheet on said nlm in side-by-side relation while said nlm is in motion; and means carried on said frame forming separate slits overlying said lenses and adapted when said frame is in said apparatus to denne separate areas on said nlm onA which said images are received, each of said areas being in the back focus of one of said lenses; said frame, lenses, and slit-forming means being removable from said apparatus as a unit, the relation position of all parts of said lens mount and the lenses carried thereby remaining nXed the while.

5. A lens mount ior use in a microrllming apparatus wherein a moving nlm is employed, said apparatus including a horizontally disposed copy feeder to feed sheet copy on the upper surface thereof past lenses nxed in relation to said copy and nlm in timed relation to movement oi said nlm; said lens mount comprising a frame adapted to be removably positioned in said apparatus; a pair of lenses secured to said frame and focussed on a moving sheet on said copy holder and forming images of said sheet on said nlm in side-byside relation while said nlm is in motion; and

means carried on said frame for supporting said nlm in the rear focal planes oi said lens vas said nlm is moved by said apparatus to expose to each lens a separate area on said nlm, said areas being spaced apart anfl of equal length, to form images on said nlm in side-by-side-relation; said frame, lens and nlm supporting means being removable from said apparatus as a unit, the relative position oi .said parts so removed remaining iixed the while.

6. A lens mount for use in inicronlming apparatus wherein a moving nlm is employed, said apparatus including a copy holder to feed sheet copy carried thereon lenses in fixed' relation to said copy and nlm in timed relation to movement of said nlm; said lens mount comprising a frame adapted to be positioned in said apparatus; a pair of lenses secured to said frame and focussed on a moving sheet on said copy feeder to form images of said sheet on said nlm in side-byside relation while said nlm is in motion; a member on said lens mount having an outer face extending' over the optical axes of said lenses, said member having slits therein traverse saidA axes, said member having a downwardly extending baffle between the inner opposed ends of said slits, member adapted to support said nlm on its outer face and position same in the back focus of said lenses, the areas defined on said slits on said nlm being aligned traversely thereon; said fram-e, lenses and slit-forming member being removable frein same apparatus as a unit, the relative position oi said parts remaining fixed the while.

VERNEUR E. PRATT.

GEORGE F.

References Cited in the nle of this patent UNTED STATES PATENTS 

